turn the key on with battery unhooked, then while focusing at the problem area, hook up the negative battery cable. This has worked hundreds of times for me when nobody around.
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Man..so d*m simple..YET i never thought of this..Pure gold!
Here i always strained and focus at the gas spray while peeping through the raised hood!

 

New FPR came in Friday and I put it in yesterday. Still black soot and the SES light came on. Problem now is my reader says it can't talk with the ECM to find out what the codes are. Has something computer related gone bad? ARGH!

 

OK, I am back into the upper plenum. The pass side now looks dry around the fpr. As I said before I am still getting black smoke which is why I am back in this thing again.
I did notice that the vacuum hose that goes from the front of the air intake to the gadget (sorry, idiot here) that mounts on the driver's side of the plenum was unplugged. Could that cause black smoke?? If that isn't the answer I may be boxing the injector up and returning it.
Anything else that could cause black smoke?

 

OK, I have now ran seafoam through a vacuum hose and it is still puffing black soot. After I did the seafoam treatment I cleared the codes and now I am getting a low O2 sensor voltage. Could the O2 sensor I just bought a few months ago be bad and cause the blazer to puff black smoke?

 

A low O2 sensor voltage code would mean a lean condition which the PCM is trying to compensate for by adding fuel. If this sensor code is for the upstream sensor (the sensor closest to the engine used for fuel management), then it stands to reason that the sensor is giving bad data to the PCM.

Now, a leak in the exhaust before the sensor could cause an artificial lean condition. Do you hear any ticking from the exhaust?

How many wires do you have on your sensor? I'm thinking it should be a 4 wire sensor. The only true way to diagnose an O2 sensor problem is to actually watch the sensor voltage as the PCM switches from lean to rich.

 

Yes it does have the 4 wire sensor. I find it interesting it is showing lean when I can almost watch the fuel gauge go down while I am driving it around trying to get it to throw codes. Oh, hold on. I think my brain just kicked in. If the O2 sensor is sending a bad lean message the injector will keep trying to send more fuel which would cause my condition????
Oh, there also is a tick coming from the engine area. Could there be a leak up front of the O2 sensor which could also throw a bad code? My brain hurts. lol

 

Yes, definitely. If there is an exhaust leak either between a head and an exhaust manifold or where the manifold mates with the y-pipe, this can cause a false lean reading by introducing oxygen into the exhaust. The closer the oxygen content of the exhaust is to the o2 content of the outside air, the lower the voltage reading from the O2 sensor.

 

It evidently was the oxygen sensor. Let this be a lesson to not buy CHEAP O2 sensors. I changed out the O2 sensor tonight and then drove it for 30 minutes and never saw a bit of smoke and had great acceleration. Thanks for all of your help.

 

Had the exact same thing happen when I changed out mine.